1. Field of the Invention
The present invention relates to an input device including an optical position detection means.
2. Description of the Related Art
Conventionally, an optical position detection device (as disclosed in, for example, Japanese Patent No. 3682109) including a plurality of light-emitting elements and a plurality of light-receiving elements is proposed as an input device. This optical position detection device is in the form of a rectangular frame comprised of a pair of L-shaped sections. The light-emitting elements are disposed in juxtaposition in one of the L-shaped sections of the rectangular frame, and the light-receiving elements opposed to the light-emitting elements are disposed in juxtaposition in the other L-shaped section thereof. The rectangular frame-shaped optical position detection device is placed along the periphery of a rectangular display. Information such as a character is inputted to the optical position detection device and is caused to appear on the rectangular display by moving a pen within the rectangular frame of the optical position detection device.
Specifically, the light-emitting elements cause light beams to travel in a lattice form within the rectangular frame. When a pen is moved within the rectangular frame, some of the light beams emitted from the light-emitting elements are intercepted by the tip of the pen. The light-receiving elements opposed to the light-emitting elements sense the interception of light beams to thereby detect the path of the tip of the pen (input information such as a character). The path is outputted as a signal to the rectangular display.
The light-emitting elements and the light-receiving elements of the optical position detection device have a certain amount of thickness, and the optical position detection device includes the light-emitting elements and the light-receiving elements disposed in juxtaposition in the form of a frame. For this reason, the frame is accordingly thick. To reduce the thickness of the frame, an input device including an optical waveguide used for the frame has been proposed (for example, Japanese Patent Application No. 2011-139481).
FIG. 7A is a plan view schematically showing the conventional input device, and FIG. 7B is a sectional view showing the conventional input device more schematically (although the positions of a light-emitting module 5 and a light-receiving module 6 are shown as differing from those in FIG. 7A for the purpose of showing more schematically). As shown in FIGS. 7A and 7B, the input device includes a rectangular frame-shaped optical waveguide W0 having a hollow input-use interior S0, and the light-emitting and light-receiving modules 5 and 6 connected to the optical waveguide W0. The light-emitting module 5 is configured such that a light-emitting element is mounted on a wiring board, and the light-receiving module 6 is configured such that a light-receiving element is mounted on a wiring board. The optical waveguide W0 and the light-emitting and light-receiving modules 5 and 6 are provided on the front surface of a rectangular frame-shaped retainer plate 70 having the hollow input-use interior S0, and are covered with a rectangular frame-shaped protective plate 80 having the hollow input-use interior S0.
The rectangular frame of the optical waveguide W0 is comprised of a pair of L-shaped sections. One of the L-shaped sections serves as a light-emitting side A, and the other L-shaped section serves as a light-receiving side B. In the rectangular frame-shaped optical waveguide W0, an under cladding layer 1 is in the form of a rectangular frame comprised of a pair of L-shaped sections. Light-emitting cores 2a are disposed in a divided manner on a surface of one of the L-shaped sections of the rectangular frame of the under cladding layer 1, and light-receiving cores 2b are disposed in juxtaposition on a surface of the other L-shaped section thereof. An over cladding layer 3 is formed on the surface of the under cladding layer 1 so as to cover the light-emitting cores 2a and the light-receiving cores 2b. The front end surfaces of the respective light-emitting cores 2a and the front end surfaces of the respective light-receiving cores 2b are positioned on inner edges of the pair of L-shaped sections (the inner periphery of the rectangular frame), and are in opposed relation to each other. An edge portion of the over cladding layer 3 covering the front end surfaces of the cores 2a and 2b is in the form of a convex lens portion 3a having a substantially quadrantal curved surface as seen in sectional side view.
A connection between the optical waveguide W0 and the light-emitting module 5 is established, with a light-emitting section of the light-emitting element connected to the rear ends of the respective light-emitting cores 2a. A connection between the optical waveguide W0 and the light-receiving module 6 is established, with a light-receiving section of the light-receiving element connected to the rear ends of the respective light-receiving cores 2b. Light beams H from the light-emitting section of the light-emitting element pass through the light-emitting cores 2a, and exit the front ends of the light-emitting cores 2a. Upon exiting, the light beams H travel in a lattice form within the rectangular frame (the hollow input-use interior S0) of the rectangular frame-shaped optical waveguide W0. Then, the light beams H enter the front ends of the light-receiving cores 2b, pass through the light-receiving cores 2b, and reach the light-receiving section of the light-receiving element.
In general, the light-receiving element is greater in size than the light-emitting element. The light-receiving module 6, in general, is accordingly greater in size than the light-emitting module 5. Also, the optical waveguide W0, in general, is made thin. Because of these facts, there are cases where the light-receiving module 6 protrudes downwardly from the optical waveguide W0 (toward the retainer plate 70) when the light-receiving module 6 is connected to the optical waveguide W0. In such cases, as shown in FIG. 7B, the retainer plate 70 is made thick, and a through hole 70b or a recess is formed in part of the retainer plate 70 corresponding to the light-receiving module 6 to receive the protruding part of the light-receiving module 6 therein. In this manner, the light-receiving module 6 is prevented from protruding from the back surface of the retainer plate 70. In this conventional input device, the light-emitting module 5 also protrudes downwardly slightly from the optical waveguide W0. A through hole 70a or a recess is formed in the retainer plate 70 to receive the protruding part of the light-emitting module 5 in a manner similar to the protruding part of the light-receiving module 6.
However, when an inputter (user) places the input device, for example, on a paper sheet K and inputs a character or the like with a pen P into part of the paper sheet K revealed within the hollow input-use interior S0 where the light beams H travel in the lattice form as mentioned above, the retainer plate 70 made thick as mentioned above causes the light beams H to travel in a vertical position high above the surface of the paper sheet K. If the inputter moves the tip of the pen P out of contact with the surface of the paper sheet K with the intention of stopping the input operation, the tip of the pen P continues intercepting light beams, so that the path of the tip of the pen P out of contact with the surface of the paper sheet K is inputted despite the intention of the inputter. To stop the input operation, it is hence necessary for the inputter to move the tip of the pen P far from the surface of the paper sheet K. This results in an unnatural input operation. The conventional input device still has room for improvement in this regard.